NISSAN ALMERA AIR FILTER PROBLEM

2001 Nissan Almera • 53,500 miles

I drive a 2001 Nissan Almera 1.5 Petrol. It runs fine, but I think it's a bit heavy on fuel. Around 21 miles per gallon. Mostly town driving. Also, only occasionally, it loses power. This only happens when pulling off in first gear. Even with my foot flat on the accelerator, it struggles to gain speed. It runs fine on motorway. Changed plugs, air filter and cleaned injectors. Difficult to check fault codes as problem only occurs occasionally.